Blinking light control arrangement



July 4, 1967 H- DOMANN ETAL BLINKING LIGHT CONTROL ARRANGEMENT FiledSept. 25, 1963 2 23 Z8 2 73 i, X 5 ,46 I3 w 3' 4 i F a a 3,329,858Patented July 4, 1967 4. fire 3,329,868 BLINKING LIGHT CONTROLARRANGEMENT Helmet Domann and Heinz Miiller, Stuttgart, Germany,assignors to Robert Bosch G.m.b.H., Stuttgart, Germany Filed Sept. 25,1963, Ser. No. 311,545 Claims priority, applicatigg (gzrmany, Sept. 29,1962,

9 12 Claims. (Cl. 315225) The present invention concerns a blinkinglight control arrangement, particularly for motor vehicle signal lights,where by operation of a switch selectively one or another group ofsignal lamps is caused to issue blinking signals while imultaneously atell-tale lamp is caused to indicate to the operator that the signallamps issue blinking light signals.

It is one object of the invention to provide for an arrangement whereinthe blinking light control comprises a multivibrator which controls theswitching operation for the signal lamps at a frequency which increasesnoticea'bly if in any one of the groups of signal lamps which areswitched on one lamp breaks down.

It is another object of this invention to provide for an arrangement asset forth above in which the multivibrator is capable of operating onlywhen the operating circuit of one of the groups of signal lamps isrendered operative by actuation of the group selector switch.

It is another object of the invention to provide for arrangements as setforth above which are comparatively very simple in structure andentirely reliable in operation.

With the above objects in view the invention includes a blinking lightcontrol arrangement, particularly for motor vehicle signal lights,comprising, in combination, a source of electric energy; work circuitmeans connected with said source and comprising lamp means, firstnormally open switch means movable to closed position for rendering saidcircuit means operative, and electrically controllable normallynon-conductive second switch means intermittently changeable toconductive condition; a stable multivibrator means connected with saidsource and including first and second transistor means in pushpullconnection, one thereof being controllingly connected with, said secondswitch means for intermittently changing the latter betweennon-conductive and conductive condition; first control resistor meansconnected between one terminal of said source and said multivibratormeans for increasing the frequency of the multivibrator action inresponse to a decrease of the current flowing through said first controlresistor means; second control resistor means connected in said workcircuit means for producing at one of its terminals a potentialdepending upon the current passing through said lamp means when saidfirst and second switch means are in conductive condition; and thirdtransistor means having an output connected with said first controlresistor means and having an input connected with said terminal of saidsecond control resistor means, said third transistor means feedingthrough said first control resistor means a current varying with avariation of said potential at said input, so that when said currentflow through said lamp means decrease below a predetermined value andsaid potential is correspondingly varied, the frequency of themultivibrator action is increased.

The novel features which are considered as characteristic for theinvention are set forth in particular in the appended claims. Theinvention itself, however, both as to its construction and its method ofoperation together with additional objects and advantages thereof, willbe best understood from the following description of specificembodiments when read in connection with the accompanying drawing, inwhich:

FIG. 1 is a schematic circuit diagram of one embodiment of the inventionincluding a multivibrator controlling an electromagnetic relay;

FIG. 2 is a similar schematic circuit diagram illustrating a secondembodiment of the invention including a multivibrator controlling acontrolled transistor acting as a switch; and

FIG. 3 is a schematic circuit diagram illustrating a modification of thearrangement according to FIG. 2.

The illustrated embodiments refer particularly to an arrangement in amotor vehicle wherein two groups 10 and 11 of the direction signallights are provided, each group comprising a pair of signal lamps, theparticular group of signal lights to be operated being selectable Ibyactuation of a normally open selector switch 14 which is in circuit witha tell-tale lamp 12, a storage battery 16 and a main switch 15 which isusually coupled with the ignition switch of the vehicle. In order tounderstand the operation of the arrangements described further below itis to be noted that if the battery 16 furnishes 6 volts the resistanceof each of the signal lamps would be about 2 ohms and thus the totalresistance of each group 10 or 11 would be 1 ohm. In contrast therewiththe resistance of the tell-tale lamp 12 is many times larger, namely ofthe order of 22 ohms.

Referring now to FIG. 1, it can 'be seen that the circuit arrangementcomprises a work circuit connected with the battery 16 and main switch15 and comprising at least one of the lamp groups 10 or 11, the selectorswitch 14 and another normally non-conductive switch including a movablecontact member 13' and a stationary contact 13" cooperating with eachother and actuated by a relay coil 13. The relay coil 13 is connectedfor intermittent energization with an astable multivibrator of basicallyknown design but supplemented by components in accordance with theinvention. The multivibrator circuit includes a first transistor T and asecond transistor T coupled with each other crosswise by means ofcapacitors 35 and 36, respectively. The output of the transistor T isconnected by line 29 with the coil 24 of the relay 13 for energizing thelatter whenever the transistor T is in conductive condition. Themultivibrator circuit is connected with the battery 16 by lines 18 and23. A third transistor T is provided which serves two purposes, namelyfirst to prevent operation of the multivibrator unless the switch 14 isin one of its conductive positions, and second, for causing a noticeableincrease of the operational frequency of the multivibrator whenever oneof the two signal lamps forming part of a group 10 or 11 thereof whichhas been switched on by the switch 14 should break down and be innon-operative condition.

When the main switch 15 is closed, the line 18 starting at thestationary contact 17 of switch 15 applies positive potential to theemitters of the three transistors T T and T The movable arm of theselector switch 14 is connected by line 19 with the stationary contact13" of the relay 13 the movable contact 13' whereof is connected via acontrol resistor 20 with the positive line 18 and simultaneously via aresistor 21 with the base of the transistor T For reasons explainedfurther below the resistance of the resistor 20 is very small and in thepresent example amounts to only .07 ohm. The tell-tale lamp 12 isconnected directly between the lines 18 and 19. In the describedexamples all the transistors are of the PNP type. Assuming that thetransistor T is a germanium transistor, it has to be taken intoconsideration that this type of a transistor is greatly dependent onoperating temperature. Therefore in this case a temperature-dependentresistor 22 is connected between line 18 and a junction point betweenthe resistor 21 and the base of the transistor T so that in this mannerthe reactions of this transistor to temperature changes are compensated.

The negative line 23 is taken from the negative terminal of the battery16 to one terminal of the relay coil 24 and to the four resistors 25,2s, 27, 2d. The second terminal of the relay coil 2 is connected vialine 29 with the collector of the transistor T while the other end ofthe control resistor 25 is connected by a line fit) with the collectorof the third transistor T The other end of the resistor 26 is connectedby a line 31 with the base of the first transistor T the other end ofthe resistor 27 is connected by a line 32 with the base of the secondtransistor T and the other end of the resistor 28 is connected by line33 with the collector of the first transistor T A resistor 34 ofcomparatively high ohmic value is connected between the lines 29 and 3t)and constitutes together with the above-mentioned control resistor 25 avoltage divider the junction point between the resistors 25 and 34 beingconnected with the collector of the transistor T In the usual manner acapacitor 35 is connected between the lines 36 and 31 and a secondcapacitor 36- is connected between the lines 32 and 33. It is advisableto connect a diode 24' in parallel with the relay coil 24. If it is notnecessary to obtain a steep rise of the current flowing through thetransistor T when the latter is rendered conductive, the above-mentionedresistor 34 can be omitted.

The arrangement according to FIG. 1 operates as follows:

When the main switch is closed but switch 14 is in non-conductiveposition then both transistors T and T are conductive while the thirdtransistor T is non-conductive. Consequently, the capacitor 35 is nowcharged and the capacitor 3% is almost discharged. Due to theconductivity of the transistor T the relay coil 24 is energized andtherefore the relay contacts 13 and 13" moved into mutual engagement.

If now while the main switch 15 is still in closed position the selectorswitch 14 is moved from its idle position into either one of itsoperative positions, e.g. into that shown in dotted lines so as to closethe circuit for the lamp group it}, then current flows from the positiveterminal of the battery 16 through the resistor 26 and switches 13, 13and T4 to the signal lamps 1t) and back to the negative terminal of thebattery 16. Consequently the lamps of the group 10 furnish a lightsignal while the telltale lamp 12 remains dark because substantially thesame potential exists at both its terminals. In view of the voltage dropdeveloping across the control resistor 2% the transistor T becomesconductive and operation of the multivibrator is started. In a wellknown manner the transistors T and T operate in push-pull fashion.Assuming that at a given moment transistor T is conductive andtransistor T is non-conductive, then the capacitor 36 is fully chargedwhile, on the other hand, current still fiows through the relay coil 24and line 23 back to the negative terminal of the battery 16. However thecapacitor 35 discharges across the resistor 26. After sufficientdischarge the potential at the base of the transistor T becomes negativerelative to its emitter and consequently the transistor Tbecomesconductive. Now the capacitor 36 is charged and the potential atthe base of the transistor T is rendered more positive. Consequently thetransistor T is rendered nonconductive and the capacitor 35 dischargesacross resistor 27. No current flows through the relay coil 24 any moreso that its relay contact 13' disengages from the stationary contact 13"under the action of the return means not shown, so that the circuit forlamp group 10 which was selected by the setting of the switch 14 isinterrupted. The lamps 10 go out but the tell-tale lamp 12 now radiateslight because, in view of the above indicated relation between theresistances of lamp 12, on one hand, and lamps it on the other hand, thevoltage drop is distributed accordingly between these different types oflamps.

As the capacitor 36 discharges the potential at the base of thetransistor T becomes negative relative to its emitter. Consequently thetransistor T becomes conductive and the capacitor 36 is charged again.The potential at the base of the transistor T becomes now positivewhereby the transistor T is rendered non-conductive. At the same timeagain current flows from transistor T through the relay coil 24 so thatthe relay 13 is energized and the contact members 13 and 13 are broughtinto engagement. Hereby the operating circuit for the lamp group It isagain closed because the selector switch 14 is still in itscorresponding position. The lamps of the group It radiate light whilenow again the tell-tale lamp 12 goes out because it is shunted by theparallel circuit through resistor 2th and closed switch 13', 13".

Hereafter the above described cycle repeats as long as, with the mainswitch 15 in closed position, the selector switch 14 is in one of itscircuit closing positions.

As far as the third transistor T is concerned it can be seen that itsinput i.e. its base is connected with the resistor 20 through whichflows the current which operates the lamp group W or 11 whichever isplaced in the circuit by actuation of the selector switch 14. Theconductivity of the transistor T depends therefore on the voltage dropacross the resistor 2t) which depends, in turn, on the amount of saidcurrent flowing therethrough. It is therefore clear that the transistorT is rendered conductive and non-conductive alternately at the samerhythm as the intermittent energization of the respective lamp group andconsequently in synchronism with the transistor T of the multivibrator.

In case in either one of the lamp groups 10 and 11 one of the lampsshould break down and become inoperative the resistance across theparticular lamp group is correspondingly increased and the current flowreduced so that correspondingly the voltage drop across the resistor 20will not sufiice for rendering the transistor T sutficiently conductive.This reduces the flow of current through transistor T and controlresistor 25 and consequently also the voltage drop across the resistor25. The result is, as can be seen, that the transistor T will be keptnon-conductive for a shorter period of time than before and this causesa reduction of the time period during which the respective lamp group orrather the lamp remaining operative therein is energized. On account ofthe reduction of the non-conductive period of the transistor T thecapacitor 36 which determines the dark period of the respective lampgroup is charged to a lesser degree so that the non-conductive period ofthe transistors T is also shortened and consequently also the darkperiod of the respective lamp or lamp group is shortened.

The shorter duration of the non-conductive periods of the transistors Tand T of the multivibrator has the effect that the operating frequencyof the multivibrator increases to more than twice its normal valuewhenever one of the two lamps of the selected group 10 or 11 breaksdown. This fact would in this case be indicated to the operator by acorresponding increased frequency of the blinking of the tell-tale lamp12.

Since it is also desirable that the multivibrator oscillates afterclosing the main switch 15 only when the selector switch 14 is movedinto one or the other of its circuit closing positions, it is necessarythat in the abovementioned voltage divide-r located in the outputcircuit of the transistor T the resistance of the resistor 34 is veryconsiderably larger than that of the control resistor 25, preferably atleast 15 times as large as the resistance of the resistor 25. The resultof this is that when the transistor T is rendered non-conductive by theselector switch 14 being in neutral position the voltage drop across thecontrol resistor 24 is very small. Under these circumstances thenon-conductive period of the transistor T will not sufiice forpermitting a sufiicient charge of the capacitor 36 so that also thenon-conductive period of the transistor T decreases to such an extentthat both transistors T and T of the multivibrator re main constantly inconductive condition as long as the selector switch 14 is not moved toone of its circuitclosing positions.

The sec-0nd embodiment illustrated by FIG. 2 differs from the abovedescribed embodiment mainly in that the electromagnetic relay 13 isreplaced by a control transistor T The relay coil 24 of the relay 13 isreplaced by a resistor 37. The emitter of the transistor T is notconnected as in FIG. 1 with the positive line 18 but instead with thebase of the transistor T The collector of the transistor T is connectedvia line 19 with the selector switch 14 while the emitter of thetransistor T is connected directlywith the control resistor 20 and alsovia an auxiliary resistor 21 with the base of the transistor T Thearrangement according to FIG. 2 operates as follows:

When the main switch is closed but selector switch 14 is in its neutralposition both transistors T and T are in conductive condition. However,the transistor T must be selected according to its parameters in such amanner that its base-emitter current is suflicient for rendering thetransistor T completely conductive. If now the selector switch 14 ismoved e.g. into the circuitclosing position indicated by a dotted lineso as to cause energization of the lamp group 10, then the transistor Tis capable of carrying an emitter-collector current. Consequently thelamps of the group 10 are energized by a flow of current passing throughthe control resistor and the transistor T is rendered fully conductiveby the voltage drop of about .5 volt across the control resistor 20 andcorrespondingly varying the potential at the base of transistor TThrough the conductivity of transistor T 3 the potential of line 30rises abruptly so as to become equal to that of the positive line 18.This jump of potential is transmitted by the capacitor 35 to the base ofthe transistor T whereby the latter is rendered non-conductive.Consequently the multivibrator comprising the transistors T and T startsto oscillate. From here on the procedure and ope-ration is identicalwith that described above in reference to the arrangement according toFIG. 1. a

The modification according to FIG. 3 differs from the embodimentaccording to FIG. 1 in that the electromagnetic relay 13 is replaced bytwo transistors T and T At the same time the series connection of thetransistors T and T of FIG. 2 is voided. The relay coil 24 is replacedas in the case of FIG. 2 by the resistor 37. However the emitters ofboth transistors T and T are connected with that terminal of the controlresistor 20 which is connected with the base of transistor T Thecollector of the transistor T is connected with the selector switch 14while its base is connected via an auxiliary transistor 38 with thecollector of the transistor T The base of transistor T is connected withthe collector of transistor T and at .the same time with a junctionpoint between the resistor 34 and the additional resistor 37. Finally,the collector of the transistor T is connected via an auxiliary resistor29 with the negative line 23 of the arrangement. On account of thisarrangement the transistor T operates in phase opposition to thetransistor T While transistor T operates in phase opposition to thetransistor T and therefore in phase with the transistor T Thus, it canbe seen that the effect of the circuit according to FIG. 3 is generallythe same as that of the embodiments of FIGS. 1 or 2.

It may be added that theoretically the resistor 34 could be dispensedwith and a satisfactory operation of the circuit arrangement could beobtained, provided that it is not deemed necessary to provide for asteep rise of the current furnished upon conductivity of transistor Tand a steep drop of the current upon change of transistor T tonon-conductivity. In this case the capacitor 35 would be connected onlydirectly with the collector of the transistor T which becomes conductiveonly after the relay 13 has been energized. Consequently, the feedbackfrom transistor T to transistor T will be the more substantial thesmaller is the resistance of resistor 34. On the other hand, it isnecessary that the resistance ratio within the voltage divider 25, 34 isas small as possible in order to make sure that the capacitor 34 will becharged to almost the full voltage of the battery 16. Therefore areasonable compromise between these two desirable conditions is theabove-mentioned resistance ratio of 1:15.

It will be understood that each of the elements described above or twoor more together, may also find a useful application in other types ofblinking light control arrangements particularly for motor vehiclesignal lights, differing from the types described above.

While the invention has been illustrated and described as embodied in ablinking light control arrangement particularly for motor vehicle signallights including an astable multivibrator, it is not intended to belimited to the details shown, since various modifications and structuralchanges may be made Without departing in any way from the spirit of thepresent invention.

Without further analysis the foregoing will so fully reveal the gist ofthe present invention that others can by applying current knowledgereadily adapt it for various applications without omitting featuresthat, from the standpoint of prior art, fairly constitute essentialcharacteristics of the generic or specific aspects of this inventi-onand, therefore, such adaptations should and are intended to becomprehended within the meaning and range of equivalence of thefollowing claims.

What is claimed and desired to be secured by Letters Patent is:

1. A flashing light arrangement comprising, in combination, incandescentlamp means adapted to operate in flashing manner; a source of electriccurrent; an electric circuit connecting said source of electric currentto said lamp means; interrupter means associated with said electriccircuit for interrupting operation of said incandescent lamp means;oscillator means arranged in said circuit for intermittently actuatingsaid interrupter means so that said source of electric currentintermittently actuates said lamp means, resulting in flashing thereof;indicator means actuated by current passing through said electriccircuit so as to deliver periodic indications at a frequency whichcorresponds to the frequency of flashing of said incandescent lampmeans; means for varying the frequency of oscillation of saidoscillator; and actuating means cooperating with said electric circuitfor automatically actuating said means for changing the frequency ofsaid oscillator whenever the electric resistance of said lamp meanschanges.

2. A flashing light arrangement according to claim 1, wherein saidoscillator means is an astable multivibrator.

3. A flashing light arrangement according to claim 1, wherein saidoscillator means is a transistorized astable multivibrator including twotransistors operating in pushpull mode.

4. A flashing light arrangement according to claim 1, wherein saidactuating means is a transistor circuit sensitive to variation ofelectric current through said lamp means.

5. A flashing light arrangement according to claim 1, wherein saidactuating means is a transistor circuit sensitive to variations in thecurrent through said lamp means and causing the frequency of saidoscillator to increase when the electrical resistance of said lamp meansis substantially increased.

6. A flashing light arrangement according to claim 1, wherein said lampmeans comprises a first and second lamp arrangement, and switching meansconnected to said lamp arrangements for selecting one thereof asdesired.

7. A flashing light arrangement according to claim 6, wherein said firstand second lamp arrangement each has at least one lamp adapted tooperate in a flashing manner.

8. A flashing light arrangement according to claim 5, including meansfor compensating impedance variations in said transistor circuit whichare due to thermal consaid source of electric current to connect .on onehand ditions, thus maintaining the impedance in said transistor a discnnect on t e other hand said source of electrlc circuit substantiallyconstant. Current Wlthln 531d arrangement- 9. A flashing lightarrangement according to claim 1,

including relay means arranged in said electric circuit 5 References(mad and operated by said oscillator means, said relay means UNITEDSTATES PATENTS operating said interrupter means upon being actuated by2,891,195 6/1959 Smyth 315 20( said oscillator means. 2,972,706 2/1961Malm 315200 10. A flashing light arrangement according to claim 1,2,973,456 2/1961 Smyth 315-200 wherein said indicator means is a lamp.10 3,002,127 9/ 1961 Grontkowski 31S-200 11. A flashing lightarrangement according to claim 1, 3,022,467 2/ 1962 Leedcr 315200wherein said source of electric current is a battery.

12. A flashing light arrangement according to claim 1, JOHN HUCKERTPrimary Exammer' including a main operating switch connected in serieswith 15 D. O. KRAFT, J. SHEWMAKER, Assistant Examiners.

1. A FLASHING LIGHT ARRANGEMENT COMPRISING, IN COMBINATION, INCANDESCENTLAMP MEANS ADAPTED TO OPERATE IN FLASHING MANNER; A SOURCE OF ELECTRICCURRENT; AN ELECTRIC CIRCUIT CONNECTING SAID COURCE OF ELECTRIC CURRENTTO SAID LAMP MEANS; INTERRUPTER MEANS ASSOCIATED WITH SAID ELECTRICCIRCUIT FOR INTERRUPTING OPERATION OF SAID INCANDESCENT LAMP MEANS;OSCILLATOR MEANS ARRANGED IN SAID CIRCUIT FOR INTERMITTENTLY ACTUATINGSAID INTERMITTENTLY ACTUTHAT SAID SOURCE OF ELECTRIC CURRENTINTERMITTENTLY ACTUATES SAID LAMP MEANS, RESULTING IN FLASHING THEREOF;INDICTOR MEANSACTUATED BY CURRENT PASSING THROUGH SAID ELECTRIC CIRCUITSO AS TO DELIVER PERIODIC INDICATIONS AT A FREQUENCY WHICH CORRESPONDSTO THE FREQUENCY OF FLASHING OF SAID INCANDESENT LAMP MEANS; MEANS FORVARYING THE FREQUENCY OF OSCILLATION OF SAID OSCILLATOR; AND ACTUATINGMEANS COOPERATING WITH SAID ELECTRIC CIRCUIT FOR AUTOMATICALLY ACTUATINGSAID MEANS FOR CHANGING THE FREQUENCY OF SAID OSCILLATOR WHENEVER THEELECTRIC RESISTANCE OF SAID LAMP MEANS CHANGES.